1. Field of the Invention
The invention relates to a step-by-step ratchet mechanism with a mount, with a hand lever that is carried on the mount in such a manner that it is pivotal about an axis of the hand lever, with a ratchet that is provided with a toothed set wheel and with an output shaft that is rotatable about an axis of the ratchet in the mount, with a pair of catches that a) are each hinged on the hand lever so as to be pivotal about an axis of the catch, b) are provided with a gear cutting that matches the set wheel and cooperates with it, c) are provided with a supporting flank that neighbors an abutment of the mount and d) are provided with a first elastic means that resiliently pretensions the two supporting flanks adjacent the abutment.
2. Description of the Prior Art
In practice, this step-by-step ratchet mechanism, which has been proposed by DE 44 00 910 A1, on principle proved its worth. Each gear cutting has only one unique tooth that is not in engagement with the faces of the set wheel""s teeth when the hand lever is in its neutral position. On pivoting the hand lever, one of the two teeth contacts one of the faces of the set wheel""s teeth and causes said wheel to rotate. The ratchet provided is a silent ratchet, more specifically a grip roller freewheel, and reference is made in this connection by way of example to WO 9941101.
In this step-by-step ratchet mechanism of the art the hand lever normally is in its neutral position in which it is kept by elastic means. By pushing the hand lever in one direction of rotation, the ratchet is unlocked and the output shaft is rotated in one direction. By repeatedly pushing the hand lever in the same direction of rotation, the adjustment procedure is carried on. By pivoting the hand lever in the other direction, in most cases by pulling the hand lever upward, adjustment of the output shaft is achieved in the other direction of rotation. The step-by-step ratchet mechanism is more specifically intended to be used in devices for adjusting vehicle seats.
In the step-by-step ratchet mechanism of the prior art the maximum angle of rotation of the set wheel that may be achieved in one travel of the hand lever is limited by the fact that only one tooth of the gear cooperates with only one gear of the set wheel at a time, and that, after a certain angle of rotation, it is removed from engagement. On return of motion of the regulating forces on the hand lever the behavior needs improvement as well.
This is where the invention comes to bear. In view of the step-by-step ratchet mechanism of the type mentioned above, it is an object of the present invention to provide improvement thereof in such a manner that the set wheel may be rotated up to a maximum rotation depending on the traveling angle of the hand lever at any travel thereof, the angle of rotation of this maximum rotation being greater than what can be achieved with the step-by-step ratchet mechanism of the prior art.
In view of the step-by-step ratchet mechanism of the type mentioned above, the solution of this object is to further provide each catch with e) a pin, to have the gear cutting designed as a toothed quadrant with several teeth, to have two mean position levers carried on the mount in such a way that they are each pivotal about an axis of the mean position levers, one mean position lever being assigned to each catch, to have the mean position levers provided with a stop flank, a stop area of the mount being assigned and adjacent to each of said stop flanks, to have a second elastic means allocated to the two mean position levers, said elastic means resiliently pretensioning the stop flank against each stop area, and to have the mean position levers provided each with a guide bight designed for receiving and guiding the pin of the corresponding catch and arranged in such a manner that its aperture faces the aperture of the other guide bight.
Both catches have several teeth arranged on a toothed quadrant, engagement between the set wheel and the hand lever with catch that can be considered part of a gear being possible within a greater pivoting angle than with the prior art mechanisms as a result thereof. The catches are controlled by the mean position levers by way of their pins. For this purpose, the mean position levers have one guide bight each, into which the pin of that toothed quadrant that is not in the drive path for the moment is moved into mesh. On returning the hand lever to the neutral position, the corresponding catch is moved in such a controlled way via the guide bight that its teeth are capable of meshing with the gear cutting of the set wheel. While the catches are hinged on the hand lever, the mean position levers are hinged on the mount.
The mean position levers each have a stop flank that is supported by a stop area of the mount in neutral position of the hand lever. The second elastic means, which is preferably designed as a tension spring, causes the two mean position levers to be pulled toward each other onto the corresponding stop area. Said stop area is preferably formed by a rib of the mount. Since the mean position levers directly act on the corresponding catches via their guide bights and the pins, the second elastic means too has a direct effect on the catches. It causes the two toothed quadrants to be elastically biased toward each other, thus competing with the first elastic means that elastically urges the two toothed quadrants away from each other. Now the geometry is adjusted in such a manner that the mean position levers abut the corresponding stop area with their stop flank when the two toothed quadrants of the catches mesh with the teeth on the set wheel. This means that the second elastic means indirectly secures the neutral position of the hand lever by way of the catches.
In a preferred embodiment, the step-by-step ratchet mechanism is substantially arranged mirror-inverted about a plane. The mirror plane is a plane running through the axis of the hand lever and the axis of the ratchet. As a result thereof, the mechanical movements are executed in a similar way in the two directions of drive.
In a preferred embodiment, the catches are provided with a bearing clearance about their axes. The two elastic means resiliently pretension the catches toward each other in such a way that, despite the bearing clearance, no clatter occurs.
If however one catch has to take over the drive, the bearing clearance is first used up prior to the drive taking place, i.e., before a torque is delivered to the set wheel by way of the catch. Among others, a forward movement is thus achieved that constitutes the first path section of the working stroke, the active actuation following only thereafter.
Accordingly, in a preferred embodiment, the axis of the catch and the area of meshing of at least one of its teeth both lie on one line that substantially runs across the faces of said tooth. The driving forces thereby do not cause the teeth of the toothed quadrant to lift off the teeth of the set wheel, but on the contrary they effect a positive engagement of the teeth of the toothed quadrant with the set wheel.
In the preferred embodiment, the pins are substantially located in the center between the axis of the catch and the area of meshing of at least one tooth of an engaged toothed quadrant. The pins are preferably positioned in such a way that they are slightly displaced toward the axis of the hand lever than toward the axes of the mean position levers.
The two catches are preferably supported by having their supporting flanks resting on an axle stub of the hand lever axis in a way analogous to the one used in the indicated, most nearly connected prior art. A silencing means, more specifically a rubber coat, is preferably provided in the supporting area. On the return motion of the hand lever after a drive, this return motion being actuated by the second elastic means, the still engaged toothed quadrant that was utilized for the previously performed drive is capable of riding over the teeth of the set wheel as a result thereof, in that the corresponding catch oscillates about its catch axis without any mechanical noise being heard when the supporting flank strikes the abutment.
In a preferred embodiment the two catches are arranged on one side of a plate-shaped mount and the mean position levers are positioned on the other side of said mount. Passages are provided for the pins in the mount, said passages surrounding the pins with a clearance. This embodiment makes simple construction possible, the catches and the mean position levers remain in immediate proximity to the mount. As a result thereof, a second bearing plate of the mount is not needed and the mean position levers and the pins can be carried on one side in the plate-shaped mount.
In a preferred embodiment, the two toothed quadrants mesh with the set wheel when the hand lever is in its neutral position. The effect thereof is that the motion of the set wheel is mechanically locked.
It has to be noticed that the cooperation between the catches and the mean position levers may also be performed in a way which is different from the described one, it may more specifically be performed in kinematic reversal. The pins may thus be provided on the mean position levers while the reception bight is formed on each catch.